Inertial exercise devices

ABSTRACT

An adjustable inertial exercise device has an elongate member with first and second threaded portions with opposite-handed threads. First and second nuts, each having at least one radial flange, are respectively rotatably engaged with the first and second threaded portions of the elongate member. A sleeve is slidably mounted over the first and second nuts. The sleeve has an internal bore with first and second bearings and at least one longitudinal groove slidably engaged with the radial flanges of the first and second nuts. Elastic resistance elements interface between the first and second nuts and the first and second bearings. Rotation of the elongate member relative to the sleeve one direction causes the nuts to move apart from one another compress the resistance elements. Rotation of the elongate member relative to the sleeve in the opposite direction causes the nuts to move toward one another and expand the resistance elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a United States national stage application of International Application PCT/US10/43235 filed Jul. 26, 2010 and entitled “Inertial Exercise Devices,” which claims priority to U.S. patent application Ser. No. 12/508,921 filed Jul. 24, 2009, entitled “Low-Impact Inertial Exercise Device,” now U.S. Pat. No. 7,927,264 issued Apr. 19, 2011. The contents of both of these prior applications are incorporated into this application by reference in their entirety as if set forth verbatim.

FIELD

The following description relates generally to exercise equipment, and more particularly to an inertial exercise device that can be used to tone the upper body.

BACKGROUND

In-home personal exercise and weight loss equipment are increasingly popular consumer products. Due to the expense of health club memberships and the time required to travel to health clubs, many people desire to exercise at home. However, many exercise machines are very expensive and require a dedicated area or room for use and/or storage. For these reasons many people do not wish to own a large exercise machine that can exercise several different muscles.

Alternatives to large home fitness machines include free weights such as dumbbells. Dumbbells have the advantage of being relatively inexpensive and easy to use. However, one drawback of dumbbells is that they are often very heavy and therefore can cause injury if a user excessively strains herself or uses poor technique. Further, each dumbbell provides a fixed amount of resistance, so a user must constantly switch between heavier in lighter dumbbells in order to vary the level of resistance. Additionally, although there are many different dumbbell exercises, each requires a slightly different technique. Many users will not be aware of all the different possible exercise, much less the proper technique for each exercise. Accordingly, many users end up doing the same simple exercises over and over again. This results in some muscles being exercised excessively, with other muscles being ignored completely.

Accordingly, there are needs for a home fitness device that is simple and safe to use, that is relatively inexpensive, that does not require a dedicated area for use or storage, and that effectively exercises several different muscles using variable resistance levels. The embodiments of a low-impact inertial exercise device disclosed below satisfy these needs.

SUMMARY

The following simplified summary is provided in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview, and is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

In one aspect of the disclosed embodiments, an inertial exercise device has an elongate member with opposing first and second end portions, and a sleeve movably coupled to the elongate member and disposed between the first and second end portions of the elongate member. A first elastic resistance element interfaces between the elongate member and the sleeve. A user-induced rhythmic movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first elastic resistance element to alternately compress and extend as the first and second end portions of the elongate member oscillate relative to the sleeve.

The first elastic resistance element may be mounted on the elongate member itself. The sleeve may have a first internal shoulder such that the first elastic resistance element is disposed between the first internal shoulder of the sleeve and the first end portion of the elongate member. The first internal shoulder of the sleeve may a slide bearing or formed as part of an internal bore of the sleeve. The first elastic resistance element may be a spring, for example a helical spring mounted coaxially with the elongate member and the sleeve.

The sleeve may further include a second internal shoulder opposite the first internal shoulder, and the exercise device may also include a second elastic resistance element mounted on the elongate member and disposed between the second internal shoulder and the second end portion of the elongate member. If so, the second elastic resistance element compresses when the first elastic resistance element extends, and extends when the first elastic resistance element compresses.

The exercise device may have a first weight attached to the first end portion of the elongate member and a second weight attached to the second end portion of the elongate member. A flexible boot may be attached to the sleeve and the first weight, the flexible boot enveloping the first elastic resistance element. The flexible boot, the first weight, and the sleeve may together form an air bellows that expels air through an aperture in the air bellows as the first elastic resistance element compresses in response to the user-induced rhythmic movement of the sleeve along the elongate member. The exercise device may also have a second flexible boot attached to the sleeve and t he second weight, the second flexible boot enveloping the second elastic resistance element. A central portion of the elongate member may have an external shoulder such that the first elastic resistance member is disposed between the external shoulder of the elongate member and the first internal shoulder of the sleeve.

In another aspect of the disclosed embodiments, an inertial exercise device has first and second terminal masses rigidly linked together by a central shaft, the first and second terminal masses and the central shaft collectively having an inertia. An actuating sleeve is slidably mounted around the central shaft and has an internal bore with a first peripheral shoulder. A first elastic resistance element is mounted on the central shaft within the internal bore of the actuating sleeve and is disposed between the first terminal mass and the first peripheral shoulder. The first and second terminal masses and the central shaft are slidable relative to the actuating sleeve between a first position with the first elastic resistance element compressed between the first terminal mass and the first peripheral shoulder and a second position with the first elastic resistance element extended. The inertia of the first and second terminal masses and the central shaft causes the actuating sleeve to oscillate relative to the first and second terminal masses and the central shaft in response to alternating rhythmic linear motion imparted to the actuating sleeve by a user of the inertial exercise device.

The internal bore of the actuating sleeve further may also have a second peripheral shoulder, and the inertial exercise device may also have a second elastic resistance element mounted on the central shaft within the internal bore of the actuating sleeve and disposed between the second terminal mass and the second peripheral shoulder. If so, the second elastic resistance element is extended when the first and second terminal masses and the central shaft are in the first position, and the second elastic resistance element is compressed between the second terminal mass and the second peripheral shoulder when the first and second terminal masses and the central shaft are in the second position.

The first and second terminal masses may be disposed within the internal bore of the actuating sleeve, and the first and second peripheral shoulders of the actuating sleeve may be opposing faces of a ridge in the internal bore of the actuating sleeve.

In yet another aspect of the present embodiments, an inertial exercise device has an actuating cylinder with opposing first and second ends and an internal bore. At least one mass is slidably mounted in the internal bore of the actuating cylinder. First and second elastic resistance elements are mounted within the internal bore of the actuating cylinder and resist motion of the at least one mass toward the ends of the actuating cylinder. The at least one mass is slidable relative to the actuating cylinder between a first position with the first elastic resistance element compressed and a second position with the first elastic resistance element extended. The inertia of the at least one mass causes the at least one mass to oscillate relative to the actuating cylinder in response to alternating rhythmic linear motion imparted to the actuating cylinder by a user of the inertial exercise device.

The inertial exercise device may also have a second mass rigidly connected to the at least one mass by a central shaft. The internal bore of the actuating cylinder may include first and second peripheral shoulders. If so, the first elastic resistance element is disposed between the first peripheral shoulder and the at least one mass, and the second elastic resistance element is disposed between the second peripheral shoulder and the second mass. The at least one mass may have first and second opposing faces such that the first elastic resistance element is disposed between the first face of the at least one mass and the first end of the actuating cylinder, and the second elastic resistance element is disposed between the second face of the at least one mass and the second end of the actuating cylinder.

In another embodiment, an adjustable exercise device includes an elongate member with opposing first and second end portions and first and second threaded portions disposed between the opposing first and second end portions. The first threaded portion has right-handed threads and the second threaded portion has left-handed threads. A first nut is rotatably engaged with the first threaded portion of the elongate member. The first nut includes at least one radial flange. A second nut is rotatably engaged with the second threaded portion of the elongate member, and the second nut also includes at least one radial flange. A sleeve is slidably mounted over the first and second nuts. The sleeve has an internal bore with opposing first and second bearings and at least one longitudinal groove slidably engaged with the at least one radial flange of the first nut and the at least one radial flange of the second nut. A first elastic resistance element interfaces between the first nut and the first bearing of the internal bore of the sleeve. A second elastic resistance element interfaces between the second nut and the second bearing of the internal bore of the sleeve. A user-induced oscillating movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first and second elastic resistance elements to alternately compress and extend as the sleeve oscillates relative to the first and second nuts and the elongate member.

The exercise device may be adjustable. For example, rotation of the elongate member relative to the sleeve in a first direction may cause the first and second nuts to move apart from one another along the elongate member to compress the first and second elastic resistance elements, and rotation of the elongate member relative to the sleeve in an opposite second direction may cause the first and second nuts to move toward one another along the elongate member to expand the first and second elastic resistance elements.

The first and second bearings of the internal bore of the sleeve may be first and second internal shoulders of the internal bore, and the first and second elastic resistance elements may be springs, which may be helical springs mounted coaxially with the elongate member and the sleeve. A first weight may be attached to the first end portion of the elongate member and a second weight may be attached to the second end portion of the elongate member. The sleeve may include a first outer portion enveloping the first weight and a second outer portion enveloping the second weight.

In another embodiment, an exercise device includes an elongate member with opposing first and second end portions and first and second threaded portions disposed between the opposing first and second end portions. The first threaded portion has right-handed threads and the second threaded portion has left-handed threads. A first nut is rotatably engaged with the first threaded portion of the elongate member. The first nut includes at least one radial flange. A second nut is rotatably engaged with the second threaded portion of the elongate member, and the second nut also includes at least one radial flange. A sleeve is slidably mounted over the first and second nuts. The sleeve includes an internal bore with opposing first and second bearings and at least one longitudinal groove slidably engaged with the at least one radial flange of the first nut and the at least one radial flange of the second nut. A first elastic resistance element interfaces between the first nut and the first end portion of the elongate member, and a second elastic resistance element interfaces between the second nut and the second end portion of the elongate member. A user-induced oscillating movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first and second elastic resistance elements to alternately compress and extend as the sleeve oscillates relative to the first and second nuts and the elongate member.

The exercise device may be adjustable. For example, rotation of the elongate member relative to the sleeve in a first direction may cause the first and second nuts to move apart from one another along the elongate member to compress the first and second elastic resistance elements, and rotation of the elongate member relative to the sleeve in an opposite second direction may cause the first and second nuts to move toward one another along the elongate member to expand the first and second elastic resistance elements. A user-induced oscillating movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first and second elastic resistance elements to alternately compress and extend as the sleeve oscillates relative to the first and second nuts and the elongate member.

The first and second bearings of the internal bore of the sleeve may be first and second internal shoulders of the internal bore. The first and second elastic resistance elements may be springs, and may be helical springs mounted coaxially with the elongate member and the sleeve. A first weight may be attached to the first end portion of the elongate member, and a second weight may be attached to the second end portion of the elongate member. The sleeve may include a first outer portion enveloping the first weight and a second outer portion enveloping the second weight.

In yet another embodiment, an inertial exercise device includes an elongate central shaft with a pair of handles mounted on opposite ends of the elongate central shaft. A pair of shoulders is mounted on the elongate central shaft adjacent to each handle. A mass is slidably mounted on the elongate central shaft between the pair of shoulders. A pair of elastic resistance elements is mounted on the elongate central shaft between the mass and each shoulder. The inertia of the mass causes the mass to oscillate relative to the central shaft in response to alternating rhythmic linear motion imparted to the central shaft by a user of the inertial exercise device.

To the accomplishment of the foregoing and related ends, certain illustrative aspects are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the claimed subject matter may be employed and the claimed subject matter is intended to include all such aspects and their equivalents. Other advantages and novel features may become apparent from the following detailed description when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of an inertial exercise device.

FIG. 2 is an illustration of the inertial exercise device of FIG. 1. in use.

FIG. 3 is an exploded view of the inertial exercise device of FIG. 1.

FIG. 4 is a cross-sectional view of one end of the inertial exercise device of FIG. 1 with the actuating sleeve spaced apart from a terminal mass.

FIG. 5 is a cross-sectional view of one end of the inertial exercise device of FIG. 1 with the actuating sleeve adjacent to a terminal mass.

FIG. 6 is a cutaway view of an alternative embodiment of an inertial exercise device.

FIG. 7 is a cross-sectional view of the inertial exercise device of FIG. 6 with the actuating sleeve adjacent to a terminal mass.

FIG. 8 is a cross-sectional view of another alternative embodiment of an inertial exercise device.

FIG. 9 is a cross-sectional view of the inertial exercise device of FIG. 8 with one of the elastic resistance elements compressed.

FIG. 10 is a cross-sectional view of yet another alternative embodiment of an inertial exercise device.

FIG. 11 is a cross-sectional view of the inertial exercise device of FIG. 10 with one of the elastic resistance elements compressed.

FIG. 12 is a graph showing a comparison of total muscle activity during a side-to-side exercise using an inertial exercise device, and a standard abdominal crunch.

FIG. 13 is a graph showing a comparison of total muscle activity during a bicep curl with an inertial exercise device and with a standard dumbbell.

FIG. 14 is a graph showing a comparison of total muscle activity during a triceps repetition using an inertial exercise device, and a standard dumbbell triceps extension.

FIG. 15 is a cross-sectional view of one embodiment of an adjustable inertial exercise device, shown in an expanded neutral configuration.

FIG. 16 is a cross-sectional view of the adjustable inertial exercise device of FIG. 15, shown in an expanded configuration at one end of sleeve travel.

FIG. 17 is a cross-sectional view of the adjustable inertial exercise device of FIG. 15, shown in a compressed neutral configuration.

FIG. 18 is a cross-sectional view of the adjustable inertial exercise device of FIG. 17, shown in a compressed configuration at one end of sleeve travel.

FIG. 19 is a cross-sectional view of the handle, elongate member, and adjustable nut of the adjustable inertial exercise device of FIGS. 15-18.

FIG. 20 shows another embodiment of an inertial exercise device.

DETAILED DESCRIPTION

In one aspect of the disclosed embodiments, an inertial exercise device has an elongate member with opposing first and second end portions, and a sleeve movably coupled to the elongate member and disposed between the first and second end portions of the elongate member. A first elastic resistance element interfaces between the elongate member and the sleeve. A user-induced rhythmic movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first elastic resistance element to alternately compress and extend as the first and second end portions of the elongate member oscillate relative to the sleeve.

FIG. 1 is an illustration of a perspective view of one embodiment of an inertial exercise device 10. In this embodiment, exercise device 10 is in the general shape of a dumbbell, having a center actuating sleeve 12 and opposing terminal masses 14 that are movably coupled to actuating sleeve 12. Flexible boots 16 extend between actuating sleeve 12 and terminal masses 14, and serve to conceal internal elements (discussed below) that functionally couple actuating sleeve 12 to terminal masses 14. Actuating sleeve 12 is provided to enable a user to grip or otherwise hold inertial exercise device 10 with one or both hands, or with another body part. The actual shape or contour of the actuating sleeve 12, terminal masses 14, and flexible boots 16 may be changed according to design preference. Therefore, modifications or alterations to the shape and appearance of inertial exercise device 10 may be made without departing from the spirit and scope of this invention. For example, the gripping portion 12 may be slimmer in size or contoured, or oriented transverse to longitudinal axis 18 of inertial exercise device 10. Similarly, inertial exercise device 10 is not necessarily shaped like a dumbbell and may, for example, be a straight cylindrical shaft.

Inertial exercise device 10 is devised to provide limited independent motion of actuating sleeve 12 relative to terminal masses 14. That is, in operation, the user grips or holds actuating sleeve 12 and “shakes” inertial exercise device 10, primarily along longitudinal axis 18, as shown in FIG. 2. Since terminal masses 14 are not rigidly fixed to actuating sleeve 12, but instead are movable relative thereto, terminal masses 14 will move out of time sync with the motion of actuating sleeve 12. In other words, due to the inertia of terminal masses 14, they will initially tend to remain at rest after the user rapidly moves actuating sleeve 12 in one direction along longitudinal axis 18. Eventually, terminal masses 14 move in the same direction as the initial movement of actuating sleeve 12, but the user then rapidly moves actuating sleeve 12 in the opposite direction along longitudinal axis 18. Due to the inertia of terminal masses 14, they will tend to remain in motion in the initial direction even after the user has rapidly moved actuating sleeve 12 in the opposite direction. Eventually, terminal masses 14 respond to the second movement of actuating sleeve 12 and begin to move in the opposite direction. Thus, the user must overcome the inertia of terminal masses 14 in order to rhythmically move or oscillate actuating sleeve 12 along longitudinal axis 18. This constant battle against the inertia of terminal masses 14 allows the user to vigorously exercise the muscles used to move actuating sleeve 12, even if the mass of terminal masses 14 is much smaller than in a traditional dumbbell.

FIG. 3 shows an exploded view of one end of inertial exercise device 10. Inertial exercise device 10 is preferably generally symmetrical so that the other end (not shown) of inertial exercise device 10 is of substantially the same construction. Actuating sleeve 12 is slidably or telescopically mounted on an elongate member such as central shaft 20. Thus, actuating sleeve 12 is free to slide back and forth along central shaft 20. To support sliding motion of actuating sleeve 12 along central shaft 20, slide bearing 24 is press fit into the internal bore of actuating sleeve 12. Thus, in this embodiment, the internal bore of actuating sleeve 12 does not directly contact central shaft 20, but instead is slidably supported thereon by slide bearing 24. Slide bearing 24 includes a peripheral flange or shoulder 25 which provides support for one end of elastic resistance element 30, which in this embodiment is a helical spring coaxially mounted on central shaft 20.

Terminal mass 14 is rigidly attached to central shaft 20 so that terminal mass 14 cannot move relative to central shaft 20. The bulk of terminal mass 14 is provided by annular inertial mass 52 which is sandwiched between inner cap 51 and outer cap 54. Outer cap 54 includes tubular protrusion 55 which receives central shaft 20. Outer cap 54 also includes one or more tabs 56 which engage with openings 64 in inner cap 51 when terminal mass 14 is assembled. Finally, outer cap 54 has one or more openings 66 for receiving fasteners 57.

Support disc 53 is mounted over tubular protrusion 55 and includes one or more threaded apertures 60. Support disc 53 serves at least two purposes. First, it provides a support surface for the outer end of elastic resistance element 30 so that elastic resistance element 30 may be compressed between slide bearing 24 and support disc 53. Second, support disc 53 is used to clamp the various components of terminal mass 14 together. Support disc 53 is disposed upon peripheral flange 62 of inner cap 51 so that when fasteners 57 are inserted through openings 66 of outer cap 54 and into threaded apertures 60 of support disc 53, support disc 53 clamps inner cap 51 to outer cap 54 with inertial mass 52 between them.

Fastener 58 passes through tubular protrusion 55 in outer cap 54 and engages with an opening in the end of central shaft 20, thereby rigidly securing terminal mass 14 to central shaft 20. Finally, end cap 59 is press-fit onto outer cap 54 in order to conceal fasteners 57. As the outer surface of inertial mass 52 may be approximately flush with the peripheral edges of inner cap 51 and outer cap 54, and end cap 59 may be approximately flush with the outer surface of outer cap 54, terminal mass 14 can be provided with a smooth and sleek external appearance.

Also adding to the aesthetic appeal of inertial exercise device 10 are flexible boots 16 extending between each terminal mass 14 and the respective end of actuating sleeve 12. Each terminal mass 14, flexible boot 16 and end of actuating sleeve 12 together collectively form an air bellows. As actuating sleeve 12 travels toward terminal mass 14, air enclosed by flexible boot 16 is expelled out of one or more apertures. This aperture may be in flexible boot 16 or in a portion of terminal mass 14. The air bellows thus formed serves both to make a distinctive sound of air rushing in and out of the aperture as actuating sleeve 12 oscillates relative to central shaft 20, and also to partially cushion each collision between the ends of actuating sleeve 12 and each terminal mass 14. In other words, the air bellows prevents the ends of actuating sleeve 12 from “banging” into terminal masses 14 and making a harsh and potentially obnoxious sound, and instead softens the collisions and makes a “puffing” or “hissing” sound. Both the external appearance of flexible boots 16 and the rushing air sound enabled by inclusion of flexible boots 16 are aesthetically pleasing features of inertial exercise device 10. Additionally, by cushioning each collision between actuating sleeve 12 and terminal masses 14, wear and tear on inertial exercise device 10 is decreased.

As shown in FIGS. 4 and 5, actuating sleeve 12 of inertial exercise device 10 is movable between two terminal positions. In the first terminal position, which is shown in FIGS. 4 and 5, actuating sleeve 12 is at its maximum distance from first terminal mass 14 a and first elastic resistance element 30 a is extended. In this first terminal position, actuating sleeve 12 is also at its smallest distance from second terminal mass 14 b and second elastic resistance element 30 b is fully compressed between second slide bearing 24 b and second support disc 53 b.

In the second terminal position, actuating sleeve 12 is at its smallest distance from first terminal mass 14 a and first elastic resistance element 30 a is fully compressed between first slide bearing 24 a and first support disc 53 a. At the same time, actuating sleeve 12 is at its maximum distance from second terminal mass 14 b and second elastic resistance element 30 b is extended. Thus, the first and second terminal positions of actuating sleeve 12 are simply inverses of one another: when actuating sleeve 12 is closest to first terminal mass 14 a (i.e. the second terminal position), first elastic resistance element 30 a is compressed and second elastic resistance element 30 b is extended, and when actuating sleeve 12 is closest to second terminal mass 14 b (i.e. the first terminal position), second elastic resistance element 30 b is compressed and first elastic resistance element 30 a is extended. Actuating sleeve 12 is slidable along central shaft 20 between these first and second terminal positions.

Although elastic resistance element 30 is shown to be compressed between slide bearing 24 and support disc 53, numerous alternative designs are available. For example, slide bearing 24 may be completely eliminated so that elastic resistance element 30 is supported by a shoulder 13 in actuating sleeve 12. This shoulder 13 is a region of the inner bore of actuating sleeve 12 of smaller diameter than elastic resistance element 30 so that elastic resistance element 30 contacts shoulder 13 and thereby resists movement of actuating sleeve 12 toward terminal mass 14. Alternatively, slide bearing 24 may be integrally formed with actuating sleeve 12. Additionally, support disc 53 may be eliminated so that elastic resistance element 30 is compressed against outer cap 54. Alternatively, support disc 53 may be replaced by a flange integrally formed or otherwise attached to the end of central shaft 20.

Another embodiment of an inertial exercise device is shown in FIGS. 6 and 7. In this embodiment, inertial exercise device 100 includes actuating sleeve 112 which is slidably mounted on central shaft 120. Terminal masses 114 a and 114 b are rigidly secured to the ends of central shaft 120 so that actuating sleeve 112 is movable relative to central shaft 120 and terminal masses 114 a and 114 b. Elastic resistance elements 130 a and 130 b are mounted on central shaft 120 inside internal bore 115 of actuating sleeve 112. Internal bore 115 of actuating sleeve 112 includes first and second peripheral shoulders 113 which contact the ends of elastic resistance elements 130. First and second peripheral shoulders 113 may be the opposing surfaces of one ridge 111 formed on internal bore 115, but may also be the surfaces of two separate ridges or protrusions formed on internal bore 115. In FIG. 6, actuating sleeve 112 is shown in its neutral position, centered between terminal masses 114 a and 114 b.

Slide bearings 124 a and 124 b are mounted on central shaft 120 and support sliding or telescoping movement of actuating sleeve 112 along central shaft 120. Slide bearings 124 a and 124 b are fixedly secured to central shaft 120 so that actuating sleeve 112 moves relative to slide bearings 124 a and 124 b when inertial exercise device 100 is used by the user. Actuating sleeve 112 therefore includes chambers 117 at both ends of inner bore 115 in order to accommodate slide bearings 124 a and 124 b as actuating sleeve 112 slides back and forth along central shaft 120. Thus, as actuating sleeve 112 is slid by the user away from terminal mass 114 a and toward terminal mass 114 b, second elastic resistance element 130 b is compressed between second peripheral shoulder 113 b and second slide bearing 124 b, thereby resisting the motion of actuating sleeve 112. When actuating sleeve 112 reaches the end of its travel toward terminal mass 114 b, as shown in FIG. 7, it can be seen that slide bearing 124 b is then at the inner end of chamber 117. Similarly, when the user reverses the motion of actuating sleeve 112 so that it slides toward terminal mass 114 a, first elastic resistance element 130 a is compressed between first peripheral shoulder 113 a and first slide bearing 124 a, thereby resisting such motion of actuating sleeve 112.

Inertial exercise device 100 optionally includes flexible boots 116 extending between terminal masses 114 a and 114 b and each respective end of actuating sleeve 112. Each terminal mass 114 a and 114 b, flexible boot 116 and end of actuating sleeve 112 together collectively form an air bellows. The functions and features of this air bellows are analogous to the air bellows discussed above in reference to the previously disclosed embodiment. As actuating sleeve 112 oscillates relative to central shaft 120 and terminal masses 114 a and 114 b, air enclosed by flexible boot 116 is expelled in and out of an aperture in the air bellows. The air bellows thus formed serves both to make a distinctive sound of air rushing out of the aperture and to partially cushion each collision between the ends of actuating sleeve 112 and terminal mass 114.

It is to be understood that other embodiments of an inertial exercise device are not necessarily in the shape of a traditional dumbbell. For example, as shown in FIGS. 8 and 9, inertial exercise device 200 is in the shape of cylinder. Actuating sleeve or cylinder 212 is a hollow cylinder having at least one central ridge 211 forming first and second peripheral shoulders 213. Central shaft 220 rigidly connects terminal masses 214 to one another. Terminal masses 214 are slidably contained inside actuating sleeve 212 so that terminal masses 214 and central shaft 220 can move in a telescopic motion from side to side inside actuating sleeve 212. This motion is resisted, however, by first and second elastic resistance elements 230, which are mounted on central shaft 220 inside actuating sleeve 212. The inner end of each elastic resistance element is braced against peripheral shoulder 213.

Thus, as the user quickly moves the actuating sleeve in one direction along its longitudinal axis 218, the inertia of terminal masses 214 and central shaft 220 will cause elastic resistance element 230 to be compressed between peripheral shoulder 213 and terminal mass 214. In other words, when the user quickly accelerates actuating sleeve 212 along its longitudinal axis 218, the inertia of terminal masses 214 and central shaft 220 will initially cause them to remain at rest relative to actuating sleeve 212. This relative motion between actuating sleeve 212 and terminal masses 214 causes one of elastic resistance elements 230 to be compressed. As the user oscillates actuating sleeve 212 along its longitudinal axis 218, each elastic resistance element is alternatively compressed in turn. FIG. 8 shows inertial exercise device 200 at rest, and FIG. 9 shows inertial exercise device 200 with one of elastic resistance elements 230 compressed after the user has quickly moved inertial exercise device 200 along its longitudinal axis 218. Although not shown in these figures, the outer surface of actuating sleeve 212 may include grip features such as indents or protrusions that help prevent inertial exercise device 200 from slipping from the user's hand.

It is to be understood that in the embodiment shown in FIGS. 8 and 9, actuating sleeve 212 may be open-ended at one or both ends. If so, terminal masses 214 may protrude partially out of the open ends of actuating sleeve 212 as terminal masses 214 oscillate inside actuating sleeve 212.

Another cylindrical shaped inertial exercise device is shown in FIGS. 10 and 11. Inertial exercise device 300 includes actuating sleeve or cylinder 312, which is again a hollow cylinder that may have a central ridge 311 forming first and second peripheral shoulders 313. However, in this embodiment, central ridge 311 and peripheral shoulders 313 may be completely eliminated because, unlike the previous embodiment, they are not needed for bracing elastic resistance elements 330. Terminal masses 314 are slidably contained inside actuating sleeve 312 so that terminal masses 314 and central shaft 320 can move in a telescopic motion from side to side inside actuating sleeve 312. This motion is resisted, however, by first and second elastic resistance elements 330, which are mounted inside actuating sleeve 312 and disposed between terminal masses 314 and the ends of actuating sleeve 312.

Thus, as the user quickly moves the actuating sleeve in one direction along its longitudinal axis 318, the inertia of terminal masses 314 and central shaft 320 will cause elastic resistance elements 330 to be compressed between the ends of actuating sleeve 312 and the outer faces of terminal masses 314. In other words, when the user quickly accelerates actuating sleeve 312 along its longitudinal axis 318, the inertia of terminal masses 314 and central shaft 320 will initially cause them to remain at rest relative to actuating sleeve 312. This relative motion between actuating sleeve 312 and terminal masses 314 causes one of elastic resistance elements 330 to be compressed. As the user oscillates actuating sleeve 312 along its longitudinal axis 318, each elastic resistance element 330 is alternatively compressed in turn. FIG. 10 shows inertial exercise device 300 at rest, and FIG. 11 shows inertial exercise device 300 with one of elastic resistance elements 330 compressed after the user has quickly moved inertial exercise device 300 along its longitudinal axis 318. Although not shown in the figures, the outer surface of actuating sleeve 312 may include grip features such as indents or protrusions that help prevent inertial exercise device 300 from slipping from the user's hand.

A variation of this embodiment is to use a single inertial element (i.e. mass) rather than two terminal masses rigidly connected to one another. For example, terminal masses 314 and central shaft 320 may completely replaced by a single cylindrical mass or slug slidably disposed in actuating sleeve 312 much like a piston. As the user oscillates actuating sleeve 312 along its longitudinal axis 318, the slug alternately compresses each elastic resistance element 330 between its outer face and the ends of actuating sleeve 312.

Although the embodiments disclosed above are either generally shaped like dumbbells or cylinders, the exact shape of the inertial exercise device is not critical. For example, the cross-section of the actuating sleeve and/or the terminal masses may not even be round, and may be polygonal such as a hexagon. Further, the inertial exercise device may be made in a wide variety of sizes, including small sizes for use with only one hand, or larger sizes for use with both hands. For example, the inertial exercise device may be approximately 12 inches long with a 1.5 inch outer diameter actuating sleeve and 3.5 inch diameter, 1.5 inch thick terminal masses. The total longitudinal travel of the actuating sleeve relative to the central shaft and terminal masses may be approximately 1.75 inches, or about 15% of the total length of the inertial exercise device. These dimensions are just one example of the possible size of an inertial exercise device, and are not to be considered limiting in any way.

The materials used to manufacture the inertial exercise device are likewise not critical. The actuating sleeve may be plastic and the central shaft may be metal, but any materials may be used. The terminal masses generally include a metal inertial mass simply to increase the inertia of the device, but any relatively dense material may be used for the inertial masses. The elastic resistance elements may be metal or elastomeric springs or cushions. The spring constant of the elastic resistance element is not critical but depends on the mass of the terminal masses used. For example, for 2.5 pound terminal masses, the spring constant of the elastic resistance element may be approximately 10 lbs/in.

One of the main advantages of the disclosed inertial exercise devices is that a user can vigorously exercise muscles without using heavy weights. The terminal masses used may be as small as one or two pounds each, but by quickly oscillating the device along its longitudinal axis, the user is constantly battling the inertia of the terminal masses and the resistance of the elastic resistance elements. Further, the inertial exercise device can be used to exercise far more muscles at one time than is possible with a standard dumbbell. For example, a user oscillating the inertial exercise device along its longitudinal axis and substantially parallel to the user's shoulders will exercise muscles in the arms, shoulders, chest and abdomen simultaneously.

Another embodiment of an inertial exercise device is shown in FIGS. 15-19. Adjustable inertial exercise device 400 is substantially the same as inertial exercise device 100 shown in FIG. 6 in most respects. Additionally, it is to be understood that any of the features of inertial exercise device 10 or inertial exercise device 100 may be incorporated into adjustable inertial exercise device 400. For example, the configuration of the terminal masses (shown best in FIG. 3) may be incorporated into adjustable exercise device 400. The main difference between adjustable inertial exercise device 400 and inertial exercise devices 10 and 100 is that adjustable inertial exercise device 400 allows the user to vary the amount of resistance provided by elastic resistance elements 430.

FIGS. 15 and 16 show adjustable inertial exercise device in a first, expanded configuration. By “expanded configuration,” it is meant that elastic resistance elements 430 are at their maximum possible length when inertial exercise device is neutral or at rest (i.e. when actuating sleeve 412 is in the middle and not forced to one side, as shown in FIG. 15). This expanded configuration is made possible due to adjustable nuts 424 which are threadably mounted on the elongate member upon which actuating sleeve 412 is slidably mounted, central shaft 420. Central shaft 420 comprises two threaded portions 421 to which each adjustable nut 424 is threadably engaged. First adjustable nut 424A is threadably engaged with first threaded portion 421A, which comprises right-handed threads. Second adjustable nut 424B is threadably engaged with second threaded portion 421B, which comprises left-handed threads. It should be pointed out that due to the “opposite-handed” threads of first and second threaded portions 421A and 421B, a given nut will travel in opposite directions when rotated in the same direction on threaded portions 421A and 421B.

To better understand the relationship of adjustable nuts 424, central shaft 420 and actuating sleeve 412, it is helpful to view the transverse cross-section of one adjustable nut 424 shown in FIG. 19. Adjustable nut 424 is threadably and engaged with central shaft 420. Adjustable nut 424 includes at least one radial flange 425 which extends radially away from the surface of adjustable nut 424. Similar to the configuration of inertial exercise devices 10 and 100, actuating sleeve 412 is slidably mounted over adjustable nut 424 and central shaft 420. However, in this embodiment, actuating sleeve 412 has an internal bore that includes at least one longitudinal groove 427. In the embodiment illustrated in FIG. 19, adjustable nut 424 has two radial flanges 425 and actuating sleeve 412 has two longitudinal grooves each slidably engaged with one of radial flanges 425. It can thus be seen that the engagement of radial flanges 425 with longitudinal grooves 427 requires adjustable nut 424 and actuating sleeve 412 to rotate in unison. In other words, if actuating sleeve 412 is rotated relative to central shaft 420, adjustable nut 424 is forced to rotate in unison with actuating sleeve 412 because longitudinal grooves 427 exert rotational force upon radial flanges 425.

Returning to FIG. 16, it can be seen that relative to FIG. 15 actuating sleeve 412 has been displaced along central shaft 420 thereby compressing elastic resistance element 424B. This displacement of actuating sleeve 412 along central shaft 420 is substantially the same as described above with reference to inertial exercise device 100. As actuating sleeve 412 is slid by the user away from terminal mass 414A and toward terminal mass 414B, second elastic resistance element 430B is compressed between peripheral shoulder 413 and second adjustable nut 424B, thereby resisting the motion of actuating sleeve 412. Similarly, when the user reverses the motion of actuating sleeve 412 so that it slides toward terminal mass 414A, first elastic resistance element 430A is compressed between peripheral shoulder 413 and first adjustable nut 424A, thereby resisting such motion of actuating sleeve 412. By rhythmically sliding actuating sleeve 412 along central shaft 420 alternately toward first terminal mass 414A and second terminal mass 414B, the user must constantly overcome the inertial of terminal masses 414 and the resistance of elastic resistance elements 430.

In this embodiment, however, it is possible to make the exercise more difficult by adjusting the position of adjustable nuts 424. To make this adjustment, the user grasps actuating sleeve 412 and one of terminal masses 414 (which are rigidly attached to central shaft 420) and then rotates the two relative to each other. As explained above, adjustable nuts 424 must rotate in unison with actuating sleeve 412 due to the engagement of radial flanges 425 with longitudinal grooves 427. Thus, as the user rotates actuating sleeve 412 relative to terminal masses 414 and central shaft 420, adjustable nuts 424 will travel toward each other along their respective threaded portions of central shaft 420. As adjustable nuts 424 move toward each other, elastic resistance elements 430 are compressed between adjustable nuts 424 and internal peripheral shoulder 413, as shown in FIG. 17. A comparison of adjustable inertial exercise device 400A in FIG. 17 with adjustable inertial exercise device 400 in FIG. 15 is illustrative. It can be seen that elastic resistance elements 430 are longer in adjustable inertial exercise device 400 than they are in adjustable inertial exercise device 400A, even though both devices 400 and 400A are shown at rest.

Thus, adjustable inertial exercise device 400 provides the user with a variable amount of resistance. According to Hooke's law, the force required to compress a spring is proportional to its spring constant times the displacement of the spring from neutral (F=kx). Because elastic resistance elements 430 are more compressed (i.e. further displaced from neutral) at rest in the configuration of adjustable inertial exercise device 400A than they are in the configuration of adjustable inertial exercise device 400, the user is required to use more force to start the rhythmic oscillation of actuating sleeve 412 in adjustable exercise device 400A than is required to start the rhythmic oscillation of actuating sleeve 412 in adjustable exercise device 400. Additionally, it can be seen that the total travel length of actuating sleeve 412 along central shaft 420 is shorter in the configuration of adjustable inertial exercise device 400A than it is in the configuration of adjustable inertial exercise device 400 because elastic resistance elements 430 become full compressed between internal peripheral shoulder 413 and adjustable nuts 424 in a shorter distance (compare FIG. 16 to FIG. 18). This means that in addition to overcoming the initial increased resistance due to the more compressed elastic resistance elements 430 in adjustable inertial exercise device 400A, the user must also oscillate actuating sleeve 412 more quickly due to the shorter total travel length of actuating sleeve 412 along central shaft 420.

It should be noted that although FIGS. 15-18 show elastic resistance elements 430 disposed between adjustable nuts 424 and internal peripheral shoulder 413, it is also contemplated that elastic resistance elements 430 could be disposed between adjustable nuts 424 and terminal masses 414, in a manner analogous to the configuration of inertial exercise device 10. In this configuration, to increase the initial resistance provided by elastic resistance elements 430, the user rotates actuating sleeve 412 relative to central shaft 420 such that adjustable nuts 424 travel away from each other rather so that elastic resistance elements 430 are more compressed at rest. In either configuration, the user can vary the resistance by rotating actuating sleeve 412 relative to central shaft 420 until adjustable nuts 424 compress elastic resistance elements 430 at rest in the precise amount the user desires for a particular workout.

Another embodiment of an inertial exercise device is shown in FIG. 20. Inertial exercise device 500 includes a pair of handles 502 mounted on opposite ends of elongate central shaft 520. Slidably mounted upon central shaft 520 in between handles 502 is mass 514. Mass 514 is slidable between shoulders 513 which are mounted on central shaft 520 adjacent to handles 502. Shoulders 513 may be formed integrally with handles 502 or may be separate components mounted upon central shaft 520. Resisting the sliding motion of mass 514 along central shaft 520 are elastic resistance elements 530. Elastic resistance elements 530 may be cylindrical helical springs mounted over central shaft 520.

To use inertial exercise device 500, a user grasps one handle 502 in each hand and begins to quickly move inertial exercise device 500 in alternating directions along the longitudinal axis of central shaft 520. This rapid alternating movement causes mass 514 to begin oscillating back and forth between shoulders 513 with its motion resisted by elastic resistance elements 530. Thus, to use inertial exercise device 500, the user must overcome both the inertia of mass 514 and the resistance of elastic resistance elements 530. In some embodiments handles 502 and/or shoulders 513 may be threadably mounted upon central shaft 520 so that the they can be moved toward or away from the center of central shaft 520. It can be seen that this movement of shoulders 513 and/or handles 502 would have the effect of increasing or decreasing the total travel length of mass 514 and the total compressive distance of elastic resistance elements 530. In other words, inertial exercise device 500 may provide adjustable resistance in some embodiments.

It should also be noted that the elastic resistance elements in any of the foregoing embodiments may be cylindrical helical springs that obey Hooke's law, namely that the force required to compress the spring is directly proportional to the distance the spring is compressed. Although this should not be taken as a limitation on the disclosed embodiments, it is a distinction from other possible elastic resistance elements such as conical springs which do not necessarily require a compressive force directly proportional to the distance of compression. By using cylindrical helical springs that obey Hooke's law, the characteristics of the rhythmic oscillation of the actuating sleeve relative to the terminal masses are improved. Whereas with conical springs the amount of force required to compress the spring may not be proportional to the distance spring is compressed (thereby making oscillations less rhythmic and more uneven), with cylindrical helical springs the force is proportional to the compression thereby enabling more rhythmic oscillations.

EXAMPLE

The benefits of the disclosed inertial exercise devices were demonstrated in a study of a total of 20 subjects (12 males, 8 females). The average age of the subjects was 25.6 years (standard deviation=4.1 years) with a minimum of 21 years and a maximum of 31 years. All subjects were relatively healthy and relatively fit. Most participated in some form of cardiovascular exercise program and/or strength training program.

Subjects were given a visual demonstration of the low-impact inertial exercise device (hereinafter “ShakeWeight” or “SW”). In addition, subjects were provided with approximately 5-10 minutes of practice time using the SW, to assure proper positioning with the device and sufficient comfort with the range of motion of the device. Once comfortable with the SW, subjects were fitted with electromyogram (EMG) electrodes on the following muscle sites: External Oblique (abdominal), Pectoralis Major (chest), Middle Deltoid (shoulder), Biceps Brachii (upper arm, front), Upper Trapezius and Middle Trapezius (shoulder girdle), Thoracic Erector Spinae (back), and Medial Tricep (upper arm, back). The ground electrode was placed on the anterior superior iliac spine. All EMG electrodes were placed on the right side of the body.

Subjects completed 12 different exercise routines, using the SW and a dumbbell as well as performing standard crunch and push-up routines. The routines included the following:

1. SW bicep shake

2. SW bicep full repetition

3. SW tricep shake

4. SW tricep full repetition

5. SW push-pull

6. SW twist side-side

7. Dumbbell bicep curl

8. Dumbbell tricep extension

9. Dumbbell one-arm row (bent over)

10. Dumbbell lateral fly standing

11. Standard floor crunch

12. Standard push-up

All dumbbell routines were performed at a uniform pace of a six-second repetition. The pace was maintained by the use of an auditory metronome that provided an audible beep every three seconds. Subjects were instructed to change direction at the sound of the beep and to maintain constant, fluid motion. Subjects completed approximately five repetitions of each of the dumbbell routines and the crunch and push-up routines. A 60-second rest was provided between routines. The SW routines were performed for approximately six seconds for routines #1, 3, 5, and 6. For routines #2 and #4 (full repetition with SW), subjects completed two full repetitions.

The total area of EMG (which is an estimate of muscle work), based on a single full repetition and based on the summation of all eight muscles, was estimated for each of the twelve exercise routines. The area is based on an established time of six seconds to complete a full repetition for each of the standard exercises. The same time normalization was established for the SW exercises.

All SW routines produced significantly greater work (EMG area) compared with any of the standard exercises (i.e., dumbbell exercises, crunch exercise, push-up routine).

Table 1 provides the average area of EMG for each of the twelve exercise routines. This area is a summation of all muscles tested. For instance, the total area for the Dumbbell Curl (DB curl) was 1209.02 microvolt-seconds (μv·s) and the total area for a single repetition of a ShakeWeight bicep curl (SW bicep curl) was 5004.54 μv·s. The SW resulted in over four times the amount of total muscle work (summing all muscles), compared with the standard dumbbell curl.

TABLE 1 Mean (μv · s) and standard deviation for each of the twelve exercise conditions, summed across all eight muscles. Routine Mean (μv · s) Std. Deviation N DB curl 1209.0167 368.99781 17 DB tricep extension 1214.9500 138.68263 18 DB lateral fly 1840.5500 187.83938 18 DB one-arm row 964.0500 156.60903 19 SW bicep fixed 3302.2430 535.94178 20 SW tricep fixed 2982.5200 258.56921 17 SW side-side twist 32043825 383.55000 20 SW push-pull 2701.9900 505.21213 16 SW bicep curl 5004.5400 789.64885 17 SW tricep extension 4307.6040 602.73946 20 Crunch 440.6333 106.18907 15 Push-up 1403.0667 429.34959 18 Total 2377.4581 322.8090 205

Regardless of the exercise routine, the SW routines consistently resulted in significantly greater motor unit recruitment (EMG) and work (area) for each muscle, when compared to the standard exercises (p<0.05).

FIG. 12 shows comparison of total muscle activity during a side-to-side exercise using an inertial exercise device, and a standard abdominal crunch. The average EMG reading for all muscles was 1120 μv for the inertial exercise device side-to-side twist, and 178 μv for the abdominal crunch.

FIG. 13 shows a comparison of total muscle activity during a bicep curl with an inertial exercise device and with a standard dumbbell. The average EMG reading for all muscles was 1167 μv for the inertial exercise device bicep curl and 933 μv for the standard dumbbell bicep curl.

FIG. 14 shows a comparison of total muscle activity during a triceps repetition using an inertial exercise device, and a standard dumbbell triceps extension. The average EMG reading for all muscles was 1123 μv for the inertial exercise device triceps repetition and 388 μv for the standard dumbbell triceps extension.

It can thus clearly be seen that the inertial exercise device is a significant improvement over these standard dumbbell exercises. Not only are more muscles exercised in each routine, but those muscles also have greater activity.

What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim. 

1-27. (canceled)
 28. An exercise device, comprising: an elongate member with opposing first and second end portions and first and second threaded portions disposed between the opposing first and second end portions, the first threaded portion having right-handed threads and the second threaded portion having left-handed threads; a first nut rotatably engaged with the first threaded portion of the elongate member, the first nut comprising at least one radial flange; a second nut rotatably engaged with the second threaded portion of the elongate member, the second nut comprising at least one radial flange; a sleeve slidably mounted over the first and second nuts, the sleeve comprising an internal bore with first and second bearings and at least one longitudinal groove slidably engaged with the at least one radial flange of the first nut and the at least one radial flange of the second nut; a first elastic resistance element interfacing between the first nut and the first bearing of the internal bore of the sleeve; and a second elastic resistance element interfacing between the second nut and the second bearing of the internal bore of the sleeve.
 29. The exercise device of claim 28, wherein rotation of the elongate member relative to the sleeve in a first direction causes the first and second nuts to move apart from one another along the elongate member and compress the first and second elastic resistance elements, and wherein rotation of the elongate member relative to the sleeve in an opposite second direction causes the first and second nuts to move toward one another along the elongate member and expand the first and second elastic resistance elements.
 30. The exercise device of claim 28, wherein a user-induced oscillating movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first and second elastic resistance elements to alternately compress and extend as the sleeve oscillates relative to the first and second nuts and the elongate member.
 31. The exercise device of claim 28, wherein the first and second bearings of the internal bore of the sleeve are first and second internal shoulders of the internal bore.
 32. The exercise device of claim 31, wherein the first and second internal shoulders are opposing surfaces of a radial flange of the internal bore.
 33. The exercise device of claim 32, wherein the first and second elastic resistance elements are mounted on the elongate member inside the internal bore of the sleeve.
 34. The exercise device of claim 28, further comprising: a first weight attached to the first end portion of the elongate member; and a second weight attached to the second end portion of the elongate member.
 35. The exercise device of claim 34, wherein the sleeve further comprises a first outer portion enveloping the first weight and a second outer portion enveloping the second weight.
 36. An exercise device, comprising: an elongate member with opposing first and second end portions and first and second longitudinal catches disposed between the opposing first and second end portions; a sleeve slidably mounted over the elongate member between the first and second end portions, the sleeve comprising an internal bore with opposing first and second threaded portions, the first threaded portion having right-handed threads and the second threaded portion having left-handed threads; an externally threaded first nut threadably engaged with the first threaded portion of the internal bore of the sleeve, the first nut comprising at least one radial lock slidably engaged with the first longitudinal catch; an externally threaded second nut threadably engaged with the second threaded portion of the internal bore of the sleeve, the second nut comprising at least one radial lock slidably engaged with the second longitudinal catch; a first elastic resistance element interfacing between the first nut and the first end portion of the elongate member; and a second elastic resistance element interfacing between the second nut and the second end portion of the elongate member.
 37. The exercise device of claim 36, wherein rotation of the elongate member relative to the sleeve in a first direction causes the first and second nuts to move apart from one another along the internal bore of the sleeve and compress the first and second elastic resistance elements, and wherein rotation of the elongate member relative to the sleeve in an opposite second direction causes the first and second nuts to move toward one another along the internal bore of the sleeve and expand the first and second elastic resistance elements.
 38. The exercise device of claim 36, wherein a user-induced oscillating movement of the sleeve along the elongate member alternatively toward the opposing first and second end portions causes the first and second elastic resistance elements to alternately compress and extend as the sleeve oscillates relative to the first and second nuts and the elongate member.
 39. The exercise device of claim 36, wherein the first and second bearings of the internal bore of the sleeve are first and second internal shoulders of the internal bore.
 40. The exercise device of claim 36, wherein the first and second elastic resistance elements are springs.
 41. The exercise device of claim 40, wherein the first and second elastic resistance elements are helical springs mounted coaxially with the elongate member and the sleeve.
 42. The exercise device of claim 36, further comprising: a first weight attached to the first end portion of the elongate member; and a second weight attached to the second end portion of the elongate member.
 43. The exercise device of claim 42, wherein the sleeve further comprises a first outer portion enveloping the first weight and a second outer portion enveloping the second weight.
 44. The exercise device of claim 36, wherein the first and second longitudinal catches of the internal bore of the sleeve are grooves in the internal bore.
 45. The exercise device of claim 36, wherein the first and second longitudinal catches of the internal bore of the sleeve are ribs in the internal bore.
 46. An inertial exercise device, comprising: an actuating cylinder having opposing first and second ends and an internal bore; at least one mass slidably mounted in the internal bore of the actuating cylinder; and first and second elastic resistance elements mounted within the internal bore of the actuating cylinder and resisting motion of the at least one mass toward the ends of the actuating cylinder; wherein the at least one mass is slidable relative to the actuating cylinder between a first position with the first elastic resistance element compressed and a second position with the first elastic resistance element extended; and wherein the inertia of the at least one mass causes the at least one mass to oscillate relative to the actuating cylinder in response to alternating rhythmic linear motion imparted to the actuating cylinder by a user of the inertial exercise device.
 47. The inertial exercise device of claim 46, further comprising a second mass rigidly connected to the at least one mass by a central shaft.
 48. The inertial exercise device of claim 47, wherein the internal bore of the actuating cylinder comprises first and second peripheral shoulders, wherein the first elastic resistance element is disposed between the first peripheral shoulder and the at least one mass, and wherein the second elastic resistance element is disposed between the second peripheral shoulder and the second mass.
 49. The inertial exercise device of claim 46, wherein the at least one mass has first and second opposing faces, and wherein the first elastic resistance element is disposed between the first face of the at least one mass and the first end of the actuating cylinder, and the second elastic resistance element is disposed between the second face of the at least one mass and the second end of the actuating cylinder. 